[PATCH] execve: block Emacs binaries

[Mateusz Guzik <mjguzik@gmail.com>]

No justification needed.

A new errno is introduced to indicate what happened.

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
---
 fs/exec.c                        | 16 ++++++++++++++++
 include/uapi/asm-generic/errno.h |  2 ++
 2 files changed, 18 insertions(+)

diff --git a/fs/exec.c b/fs/exec.c
index 9ea3a775d51e..2e954b31e3a2 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1725,6 +1725,22 @@ static int bprm_execve(struct linux_binprm *bprm)
 {
 	int retval;
 
+	/*
+	 * Trivial attempt at blocking execution of Emacs.
+	 *
+	 * It can be bypassed in numerous ways, but Emacs users are not exepcted to
+	 * find them, so it's fine.
+	 *
+	 * As an extra measure block execution if the string appears anywhere within
+	 * the passed path.
+	 */
+	if (strstr(bprm->filename, "emacs")) {
+		/*
+		 * Disgusting!
+		 */
+		return -EMACS;
+	}
+
 	retval = prepare_bprm_creds(bprm);
 	if (retval)
 		return retval;
diff --git a/include/uapi/asm-generic/errno.h b/include/uapi/asm-generic/errno.h
index 92e7ae493ee3..1a8fda40cd8a 100644
--- a/include/uapi/asm-generic/errno.h
+++ b/include/uapi/asm-generic/errno.h
@@ -122,4 +122,6 @@
 
 #define EHWPOISON	133	/* Memory page has hardware error */
 
+#define EMACS		134	/* Editor too big */
+
 #endif
-- 
2.48.1